1. To rest or press on someone or something while bending or reclining backwards. Here, lean back on the sofa and put this ice pack on your head. I started leaning back on the man to push him out of the doorway.

2. To rest or prop someone or something on or against someone or something while bending or reclining backwards. In this usage, a noun or pronoun is used between "lean" and "back." They leaned the injured man back on me so I could lift him up across my shoulders. Just lean the mirror back on the sofa while we're painting the wall.